I have a mildly built 355 sbc, hei distributor and msd 6al. I had an issue where the pulley on the crank stripped the bolts and had come off during a startup of the motor. I replaced the balancer with same size as what was on vehicle that had stripped. I had a 750 edelbrock on the car started up fine ran and had no problems. the next day I wanted to take the car out for a quick cruise and the damn thing wont fire up. it shoots fireballs out the carb, wont fire I can just crank and crank if it does fire itll sputter then backfire with mist of fuel. I pulled the 750 edelbrcok off and put a 600 edelbrock on and it does the same thing. what the hell gives? nothing has changed on the car other then swapping carbs out??? any ideas? fuel psi is at 5.5.

 

Sounds like an intake valve isn't closing.

How long since the motor was built? How long did it run right?

 

motor was built last year. it ran fine as in starting up, I haven't drove it since last year. just strange it came out of no where

 

Is your timing set correctly? I fought with timing on my motor causing the same thing you are describing.

 

I never touched the timing or distributor. only thing that has changed was the harmonic balancer and from a 750 carb to a 600 carb.

 

Verify the timing anyway. You may have inadvertently moved the distributor while working on the car. It certainly sounds like you have timing retarded too much.

 

Yup. The timing on my motor was never touched either. But when I tried to start it, it backfired though the carb.

I have mine set to a base timing of 12*, and at full advance its at 36*. Works real well.

 

ok will do

 

came home from wrk and attempted to start again. no start this time. I tried starting and it just cranks pretty fast. it getting fuel but spark was my next question. pulled a plug and they are black and soaked. can this be my misfire? and what plug would work good? I have acdelco r45t now

 

What did you find out about the spark?

Quick test, take a spark plug out, leave it in the boot, hold it next to the frame and crank the car. Make sure you're wearing a leather glove and don't touch the plug itself, just the wire. If it sparks, then you're good. If it doesn't, then you've found part of your problem.

Or you can buy a cheap little tool that you lay against the plug wire that lights up when it senses spark going through it.

By everything you've mentioned if you have spark then I'll bet when your damper broke 'your timing slipped so now your timing is off as some others here have mentioned.

You need to find TDC with number 1 piston and reset your timing and find out if you have spark or not.

 

the plugs were pretty wet. bang on table and fuel comes out so im thinking the plugs are the issue

 

You'll still want to verify timing, if its not firing at the right time you'll get wet plugs.

 

im gonna verify timing also hoping to find time tomorrow to mess with it

 

Spark plugs being fouled won't make a motor spit back through the intake. In the exhaust; yeah; intake, no. Which is not to say that your plugs are OK, or you shouldn't change em, or anything of the kind; only, that they ARE NOT capable of producing the symptom at hand. Not physically possible. Go ahead and change em, and be prepared to change em AGAIN when you find the REAL problem and they're messed up AGAIN in the EXACT SAME way they'r emessed up now.

"Timing" doesn't just up and change itself that way. "Mess with it" if you just really enjoy messing with stuff, but make sure you mark it so you can put it back, because you're going to need to do just exactly that.

Valve springs, OTOH, DO break.

See my signature for a hint as to what you should be spending your time and effort on.

 

how would a valvespring break when vehicle hasn't been on the road yet only startup to see if carb worked on car? only things changed were balancer and carb back to 600cfm carb.

 

I got spark and fuel. I checked timing with tdc and everything lines up like it should. the car only cranks and cranks and wont fire. could the timing be off even though it shows tdc normal?

 

Are you still running a module in the HEI? If yes, they are known to go and cause similar problems (usually at higher RPM).

 

Good call. This was going to be my next suggestion along with verifying fuel pressure to make sure he's actually getting gas.

The module went out in my car 20 miles from home. My phone was dead and the charger was in my other car. It was a long walk to the gas station...however, swapped in the new module which took 10 minutes and she fired right up.

 

no I don't have a module im running the msd 6al box.... not sure what else to check

 

Although uncommon, I have heard of MSD boxes going south. Check to make sure the box is getting a full and steady 12v. You may be getting spark, but it could be a very weak spark.


You may just have to start eliminating things:
1) Do a cranking compression test on all 8 cylinders to make sure a valve isn't hung open.
2) Verify that the balancer mark, the timing tab and actual TDC (use a piston stop) all agree on what zero is.
3) Check fuel pressure.
4) Check for vacuum leaks.
5) Ohm test the spark plug wires.


Electrical issues can be a bear. That's why I became a mechanical engineer instead of an electrical engineer! LOL

 

He says he verified spark. But its worth trying a different box tobsee if maybe he doesn't have enough.

Will it start if you spray it with starting fluid while cranking?

 

I went through three valve springs when I built my 355. They're mechanical and do break. Also, if your timing slipped bad enough it could have broken something.

 

haven't tried starting fluid if I hit the throttle fuel sprays into carb like supposed to/.

 

1. all cylinders equal out to about 145-150 on each cylinder
2. verified and is accurate
3. fuel psi is set at 5.5
4. replaced all lines and caps for vaccum
5. brand new wires were installed last year maybe 3 hours on them

 

Well...I am running our of suggestions!! LOL


We still need to verify that the spark we are getting is a strong spark and also the valve spring issue Sofakingdom mentioned. Swapping the 6AL box with someone as a test is the easiest way to check the box. If you check the spark at a plug (by grounding it against the frame), you should see a strong white spark...not an orange or red colored spark.

 

ya I get a nice bluish white spark when grounded. I don't kno anyone that has a 6al box so that's going to be kind of tough. im gonna pull valve covers and see what I got

 

and the starter turns fast so its not struggling to turn motor

 

got to mess with car for a few while taking a break from taken care of a sick wife. checked the valve springs look good. as rotating the engine I hear a good awful racket coming from under car. the torque convertor bolts came loose causing the starter to not be able to spin the motor freely like it should. fired up right after that. damn stupid thing I tell u

 

And there you go...all of us were wrong! LOL


Glad you got it figured out and hope the wife is feeling better really soon!!

 

thanks. I wouldn't say everyone was wrong, very helpful information was given as well as what could be wrong. thanks guys